From 7a9eacb7177b0cf100de02cda3bbf6913892fc19 Mon Sep 17 00:00:00 2001
From: Sam Watkins <sam@ucm.dev>
Date: Tue, 14 Mar 2023 03:07:02 +1100
Subject: [PATCH] Fix issue 3152 - convert nbdev directives to YAML

---
 src/core/jupyter/jupyter.ts            |  5 ++++-
 src/core/lib/partition-cell-options.ts | 11 +++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/core/jupyter/jupyter.ts b/src/core/jupyter/jupyter.ts
index 4a1d0496326..f81e398d2a8 100644
--- a/src/core/jupyter/jupyter.ts
+++ b/src/core/jupyter/jupyter.ts
@@ -375,7 +375,8 @@ export async function quartoMdToJupyter(
               }
               delete yaml[key];
             } else {
-              if (!kJupyterCellOptionKeys.includes(key)) {
+              // an option value of null means that it is an nbdev-style directive
+              if (!kJupyterCellOptionKeys.includes(key) && yaml[key] !== null) {
                 cell.metadata[key] = yaml[key];
                 delete yaml[key];
               }
@@ -844,6 +845,8 @@ export function jupyterCellOptionsAsComment(
     });
     const commentChars = langCommentChars(language);
     const yamlOutput = mdTrimEmptyLines(lines(cellYaml)).map((line) => {
+      // an option value of null means that the key is a nbdev-style directive
+      line = line.replace(/: null$/, "");
       line = optionCommentPrefix(commentChars[0]) + line +
         optionCommentSuffix(commentChars[1]);
       return line + "\n";
diff --git a/src/core/lib/partition-cell-options.ts b/src/core/lib/partition-cell-options.ts
index 9418a466493..bf85eebc3b9 100644
--- a/src/core/lib/partition-cell-options.ts
+++ b/src/core/lib/partition-cell-options.ts
@@ -64,6 +64,7 @@ export function partitionCellOptions(
             yamlOption += line[line.length - 1];
           }
         }
+        yamlOption = fixNbdevDirective(yamlOption);
         yamlLines.push(yamlOption);
         optionsSource.push(line);
         continue;
@@ -96,6 +97,16 @@ export function partitionCellOptions(
   };
 }
 
+function fixNbdevDirective(line: string) {
+  // convert non-yaml nbdev-style directives to yaml keys with a null value
+  if (line.match(/^\w+\s*$/)) {  // e.g. export
+    return line.replace(/(\s*)$/, ": null$1");
+  } else if (line.match(/^\w+\s+[^:\s]/)) {  // e.g. default_exp foo
+    return line.replace(/(\s*)$/, ": null$1");
+  }
+  return line;
+};
+
 export async function parseAndValidateCellOptions(
   mappedYaml: MappedString,
   language: string,